1. Field of the Invention
This invention relates to hollow containers and more particularly to containers of variable volume having at least one substantially rigid boundary surface. In particular, this invention is directed to variable volume containers utilizable for storing fluid ink or supplying ink to ink recording devices such as ink mosaic recorders for office machines, data printers or teleprinters.
2. Prior Art
Ink recording devices such as, for example, office machines utilizing ink mosaic recorders, jet ink printers, data printers, etc. are frequently provided with replacable and/or disposable ink storage containers. Such containers include both open and closed ink supply containers. Generally, ink supply containers of the open type utilize basically rigid walls. In such cases the volume of consumed ink is replaced in the container by in-flowing air.
Alternatively, it has been known to use basically closed ink supplied containers. Such closed supply containers have numerous advantages such as avoidance of pollution of the ink by being mixed with solid, liquid or gaseous substances. Additionally, closed containers effectively reduce or limit ink evaporation. In order to compensate for volume loss of consumed ink in such closed containers, it is necessary to design at least a part of the container wall to be movable. In practice this is meant that flexible foils which follow the escaping ink liquid are used as mobile wall components.
For example, it is known (German Offenlegungsschrift No. 2,323,762) to provide an ink supply in an ink bag constructed of flexible foil which is received between two plates of suitable shape. On the other hand, it has also been known (see for example German Offenlegungsschrift No. 2,610,518) to construct the ink supply container from two cooperating components. For example, one component could be a half-shell of substantially rigid shape and the other component a joining wall composed of a flexible foil which may be a mirror image to the rigid shell.
In such embodiments, the flexible foils must be sufficiently thin to exhibit the desired flexibility and are therefore correspondingly liable to damage thus requiring protective measures. If the flexible foils are elastically deformable they exert an elastic force upon the enclosed ink liquid which changes in dependence to the degree of expansion of the foil. Such changing pressure is undesirable for a clean printing operation. Flexible foil material which, on the other hand, is not or is only slightly elastically deformable, will fold upon itself forming folds which differ in degree of definition and in number during positional changes of the foil. During formation and release of the folds, the enclosed ink liquid may again be subject to differing forces which unfavorably influence the printing system.
It would therefore be an advance in the art to provide a flexible, collapsable ink supply container having basically stable shaped wall components and wherein the volume change occurs along predetermined fold lines substantially under conditions which are identical over the entire volume change zone.